The very first planet detected outside our solar system powerfully made clear that our prior understanding of what planets and solar systems could be like was sorely mistaken.
51 Pegasi was a Jupiter-like massive gas planet, but it was burning hot rather than freezing cold because it orbited close to its host star — circling in 4.23 days. Given the understandings of the time, its existence was essentially impossible.
Yet there it was, introducing us to what would become a large and growing menagerie of weird planets.
Hot Jupiters, water worlds, Tatooine planets orbiting binary stars, diamond worlds (later downgraded to carbon worlds), seven-planet solar systems with planets that all orbit closer than Mercury orbits our sun. And this is really only a brief peak at what’s out there — almost 4,000 exoplanets confirmed but billions upon billions more to find and hopefully characterize.
I thought it might be useful — and fun — to take a look at some of the unusual planets found to learn what they tell us about planet formation, solar systems and the cosmos.
Let’s start with the seven Trappist-1 planets. The first three were detected two decades ago, circling a”ultra-cool” red dwarf star a close-by 40 light years away. Observations via the Hubble Space Telescope led astronomers conclude that two of the planets did not have hydrogen-helium envelopes around them, which means the probability increased that the planets are rocky (rather than gaseous) and could potentially hold water on their surfaces.
Then in 2016 a Belgian team, using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, found three more planets, and the solar system got named Trappist-1. The detection of an additional outer planet was announced the next year, and in total three of the seven planets were deemed to be within the host star’s habitable zone — where liquid water could conceivably be present.… Read more